Le bassin de Tizi n'Test (Haut Atlas, Maroc) : exemple d'évolution d'un segment oblique au rift de l'Atlantique central au Trias

Abstract

Detailed mapping completed by a microtectonic study of the Tizi n'Test Triassic basin, located along the Tizi n'Test fault zone in the Moroccan High Atlas, has allowed us to improve the knowledge on the geometry of the structures and the activity of faults during the Triassic extensional events related to the rifting of the central Atlantic. The latter are reflected by the development of a rift, at present inverted and deformed by the collision of Africa and Europe, comprising kilometric-scale grabens and half-grabens bounded by major faults trending ENE–WSW, with a dip towards the NNW, and a dip-slip syndepositional motion. Inverse analysis of fault slickenside populations shows a heterogeneous Triassic state of stress. However, in the most significant measurement sites, the maximum horizontal stress σ1 is vertical, while the minimum stress σ3 is horizontal with a NW–SE trend. The strike-slip component appears to be very small during the Triassic, a noticeable fact because of the obliquity of the basin with respect to the Atlantic rift.